On Tue, 13 Nov 2007, Eric R. wrote:
>
> This may not be the smoothest way to produce the result, but here is a
> two-step solution:
>
> first find the formula within the object created by the call to glm():
>
> form <- qq["formula"] or equivalently form <- qq$formula
Oh, please , do use extractors where provided,
> then apply the function all.vars() to the result, and return the first
> element
>
> variables.in.formula <- all.vars(form)
>
> variables.in.formula[1] # will be the response variable
That's not guaranteed by any means. The response could be an expression,
not a variable. A fairly simple way is
formula(qq)[[2]]
which will produce a language object such as a name. If you want a
character string you can then use either deparse() or as.character() on
it. So something like
ff <- function(fit)
{
f <- formula(fit)
if(length(f) < 3) stop("no response")
resp <- f[[2]]
if(!is.name(resp)) stop("response is not a name")
as.character(resp)
}
> leffgh wrote:
>>
>> for example
>> glm(a~b+c+d,data=eee)->qq
>>
>> Is there a function able to return the name of the response variable?
>> suppose "ff" is the function satisfying this need,
>> ff(qq) then "a" (Not the value of a) will be returned.
>> could you tell me which is the "ff" I am looking for ?
>>
>> Thank you very much
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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